Method of shaving gears



Feb. 3, 1948. w, s, PRAEG 2,435,405

METHOD OF SHAVING GEARS Original Filed Jan. 10, 1944 4 Sheets-Sheet 1 J 1,. He.

:Nvu/rox wALTz-:R SPRAEG Mf/ 'l Feb. 3, 1948. w. s. PRAEG l 2,435,405.

' METHOD OF SHAVING GEARS Original Filed Jan. 10, 1944 4 Sheets-Sheet 2 INVENroR.

WALTER SPRAEG I7 BY ATTORNEYS Feb. 3, 1948. w. s. PRAEG 2,435,405

METHOD OF SHAVING GEARS Original Filed Jan. 10, 19.44 4 Sheets-Sheet 3 INVENTOR.

WALTER S.PRAEG l ,fr

ATTORNEYS Feb. 3, 1948. w, s, PRAEG 2,435,405

METHOD OF SHAVING GEARS Original Fviled Jan. 10, 1944 4 Sheets-Sheet 4 FIG.|4.

INVENTOA.

WALTER S4 PRAEG ATTORNEYS Patented Feb. 3, 1948 METHOD F SHAVENG GEARS Walter S. Praeg, Detroit, Mich., assigner to National Breach & Machine Company, Detroit, f Mich., a corporation-ci Michigan original application-January 1o, 1944, serial No.

.517.726, now'Patent No. 2,380,261,

dated July 10, 1945. Divided and this application March 19, 1945, Serial No. 583,433

(Cl. i90-1.6)

3' Claims. l

The invention relates to the finishing of gears and refers more particulanly to the yshaving of gears.

The invention has for one of its objects to provide an improved method oi shaving a gear which comprises relatively translating the gear and cut ter in opposite directions and relatively feeding the gear and cutter toward each other at one end only of the relative translation to thereby avoid objectionable interference or resistance to the relative feeding.

The invention has for another object to provide an improved method of shaving a gear which comprises reversing the direction of rotation of the motor for driving the cutter at one end only of the relative translation oi the gear and cutter to avoid overheating the cutter driving motor when the rate of relative translation is very fast.

The invention has for a further object to provide a method which is particularly useful in shaving a narrow face width gear, this application being a division of my Patent No. 2,380,261, granted July l0, 1945, filed January 10, 1944, and relating particularly to a method of shaving a blind gear.

These and other objects of the invention will become apparent from the following description, taken in connection with the accompanying drawings, in which Figure l is a diagrammatic front elevation oi a gear iinishing machine for carrying out the method embodying the invention;

Figure 21s a diagrammatic end elevation thereof;

Figure 3 is a diagrammatic plan View of a portion thereof;

Figures 4, 5, 6, 7, 8, 9 and 10 are diagrammatic v views illustrating successive steps of the method;

Figure 11 is a diagrammatic cross section illustrating one special use of the method;

Figure l2 is a diagrammatic view illustrating the method used in Figure 1l;

Figure 13 is a view similar to Figure 1l illustrating another special use of the method;

Figure 14 is a diagrammatic front elevation of another machine for carrying out the method.

In carrying out the method embodying the invention a circular gear-like cutter having its teeth provided with cutting edges is rotated in mesh and at crossed axes with a roughed-out gear which has been formed by hobbing or shaping a gear blank. As a result, cutting takes place over a limited contact area so that a minimum pressure is required and, as a result, a. minimum distortion takes place. During the rotation a relative latifi the gear.

eral movement or translation in opposite directions between the cutter and gear is effected and at o'ne end only oi the relative lateral movement or translation the cutter and gear are relatively fed toward each other until the desired amount of material has been removed from the gear.

During the relative lateral movement or translation in one direction following the relative feed the cutting action of the cutter is distributed from end to end oi the teeth of the gear. During the relative lateral movement or translation in the opposite direction the distance 'between the axes of the cutter and gear remains iixed so that an idling stroke occurs during which the teeth of the gear may be more highly finished. Also during the rotation and relative lateral movement or translation in opposite directions between the cutter and gearthe direction of rotation of the cutter is reversed at one end only of the relative lateral movement or translation. As a result, the rate of relative lateral movement or translation may be very fast without overheating the motor for driving the cutter.

A machine or carrying out the above method, as diagrammatically illustrated in Figures 1, 2 and 3, comprises the table i carrying the gear 2 to be shaved and the head 3 above the table carrying the circular gear-like cutter 4 and suitable gearing 5 for rotating the cutter. The cutter has its teeth formed with cutting edges extending generally parallel to the plane of rotation of the cutter. The gear and cutter mesh at crossed' axes at a limited angle preferably between 3 and 30 and the rotation of the cutter compels rotation of The gear and cutter are relatively translated in opposite directions in a plane parallel to the axis of the gear by reciprocating the table l by means of the lever 6 which is pivotally mounted between its ends at 1 and has one end 8 located between the abutments 9 upon the table and the other end eccentric Il. The gear and cutter are relatively fed toward each other by moving the head 3 downwardly towardthe table l by means of the lever I2 which is pivotally mounted between its ends at i3 and has one end I4 engaging the head and the other end I5 provided with the roller I6 engaging the cam Il. I8 is a coil spring for resiliently holding the head 3 against the end I4 of the lever.

The eccentric Il and the cam I1 are driven in timed relation to each other and the cam is constructed to effect small increments of feed of the cutter 4 toward the gear 2 at one end only of the relative translations in opposite directions.

I0 bifuroated to 'straddle the While the cam may have dierent numbers oi.' stations, it, as shown in the present instance, has eight stations, I'. 2', 3', 4', 5', 8', 1' and 3', which register with or are opposite to and engage the roller I6 at the ends of successive relative translations. More particularly, the eccentric I I is mounted on the vertical shaft I9, the upper end of which is connected to the cam I1 by the gearing 20, which latter is carried by the column of the machine. The lower end of the shaft I9 is connected by the gearing 2i to the electric motor 22.

The electric motor 23, which is connected to the gearing 5 to drive the same, is reversible to rotate the cutter in opposite directions. The operation of the motor 23 is automatically controlled in timed relation to the eccentric -Il and the cam I1 to reverse the motor and the cutter at one end only of the relative translations of the gear and cutter in opposite directions. As shown in the present instance, the cutter driving motor is reversedv by the limit switch 24 which is operated by I the eccentric I I through the bifurcated end of the lever 6.

Referring to the method of shaving, the successive steps are diagrammatically illustrated in Figures l and 2, 3, 4, 5, 6, '7, 8, 9 and 10. At the start, as shown in Figures 1 and 2, the cutter 4 and the gear 2 are in mesh at crossed axes with the cuttermainly at the left hand side of the gear and the cam in a rotative position with its station I registering with the roller I6. Also the cutter and the gear are rotating in the directions of the arrows 25 in Figure 2. During the iirst step,

the table I is moved in the direction of the arrow 26 in Figure 1 to the position illustrated in Figure 4 with the cutter 4 mainly at the right hand side of the gear 2. During this relative translation, the contact between the teeth of the cutter 4 and gear 2 progresses from the left hand end to the right hand end of the gear to distribute the shaving by the cutter over the teeth of the gear. Also during the nrst step the cam I1 is rotated to bring its station 2" in registration with the roller I6, as also shown in Figure 4. Since the cam has the same radius from the station I to the station 2' the spacing between the axes of the cutter and gear is maintained. At this time, the first cutting stroke has been completed.

During the second step, the table I is moved in the direction of the arrow 21 in Figure 4 and the cam I1 is rotated to bring the parts to the positions shown in Figure 5, at which time the cutter 4 and gear 2 are in the same relative position of translation, as shown in Figure 1, and the cam I 1 is in a position with its station 3' registering with the roller I6. During this step the axes of the cutter and gear are maintained in fixed relation until the station 3 registers with the roller I6 at the end of the stroke, the cam at this time lfeeding the cutter 4 a small increment toward the gear 2. The first idling stroke has now taken place. Also at the end of the iirst idling stroke the cutter driving motor 23 is reversed by operation of the switch 24.

The cutter having been moved a small increment toward the gear and the rotation of the cutter and gear having been reversed, the cutter effects a shaving of the teeth of the gear durin g the third step While the table I is being moved in the direction ofthe arrow 28,in Figure 5 to bring theparts-'toithe positions 'shown in Figin'e 6. At this time it will be noted that the station 4"of the cam I1 registers with the roller I6 and also that the portion-o1 the cam Including the station 4' forms part of a dwell so that during -the second cutting stroke the spacing between the axes of the cutter and gear has been maintained.

This next relative translation is the fourth step during which the table is moved in the direction of the arrow 29 in Figure 6 and the cam I1 is rotated to bring the parts to the positions shown in Figure '1. At this time the cutter and gear occupy the same relative position of translation, shown in Figure l, and the cam occupies al position with its station 5' registering with the roller I6. During this step the axes of the cutter and gear are maintained in fixed relation until the station 5 registers with the roller 6 so that the second idling stroke occurs. Upon registration of the station 5' with the roller the cutter is fed by a small increment toward the gear and the cutter driving motor is reversed.

During the iifth step relative translation oi. the cutter and gear is eiected by moving the table I in the direction of the arrow 30 in Figure '7 to effect a third shaving of the teeth of the gear by the cutter. At the end of this step the parts are in the positions shown in Figure 8 l Duringthe relative translations by' moving thel table in the direction of the arrows 3|, 32 and 33 in Figures 8, 9 and 10, respectively, the spacing between the axesk of the cutter and gear is maintained fixed ksince the portion of the cam between the stations 5' and 8' forms a dwell. As a result, the movement of the parts to the positions of translation indicated in Figures 9, 10 and 1 are mainly idling strokes during which the surfaces of the teeth of the gear are more accurately and highly iinished. It is apparent that the number of cycles, including the cutting in one direction of relative translation, and the number of cycles, including mainly idling in both directions of relative translation, may be varied.

Figures 11 and 12 illustrate diagrammatically'a special gear and also the method of shaving the gear. The gear is a blind hobbed pinion 34 having the teeth 35 which are open at one end and blind at the other end. 3B is the cutter having its teeth formed with the cuttingedges 31 extending generally parallel to the plane of rotation oi the cutter. The cutter and pinion are in mesh at crossed axes and rotated and during the rotation they are relatively translated to relatively move the cutter and gear so that the cutter successively occupies the positions shown by the full lines and the dotted lines relative to the gear, as illustrated in Figure 11. At the start the cutter occupies the .position shown in full lines in Figure 11, at which time itis mainly to the right of the lgear and at the open end of the teeth of the latter. of the axes of the cutter and gear are such that Y during the first relative translation, as indicated by the arrow 38 in Figure 12, the cutter eifects a shaving of the teeth of the gear until it reaches the relative position indicated liydoi'ntezi lines Vin Flgurelll, at which time relative translation in l' the direction of the arrow 39 in .Figure 12 takes place, during which the spacing between the axes of the cutter and gear is maintained. When the cutter again reaches the position` indicated by The relative positions anales the full lines in Figure 11, relative feed of the cuttei .and gear is effected and the direction oi rotation is reversed so that upon the next relative translation in the direction of the arrow in Figure l2 the teeth of the gear are cut. During the relative translation in the opposite direction, as indicated by the arrow Il in Figure l2. the spacing between the axes of the cutter and gear is maintained and when the cutter again reaches the position indicated by the full lines in Figure il relative feed of the cutter and gear takes place and the direction of rotation is reversed so that upon relative translation in the direction of the arrow 42 in Figure 12 the teeth of the gear are cut. Then during the relative translations in the directions of the arrows 48. llt and it in Figure 12 the spacing between the axes of the cutter and gear is maintained so that the relative translations are idling strokes used to finish the surfaces of the gear teeth, the last 'two strokes being carried out with the cutter and gear rotating in a direction opposite to that of the preceding stroke. .After the last relative translation the gear may be returned to its original position.

Figure 13 shows another special construction of gear for the shaving of which the method useful. A

embodying the invention is particularly in this instance the gear is c, narrow face width gear 13B, thevteeth of which are to be shaved by the cutter d? having its teeth provided with cutting edges substantially parallel to the plane ci rotation of the cutter. The gear and cutter are arranged in mesh and at crossed ares with the center line lil of crossed aries near one end of the cutter, While the cutter and gear are being rotated, they are also relatively translated to relatively move the same so that the cutter moves from the position indicated by ruil lines to the position indicated by dotted lines,` relative to the gear so that the center of crossed ailes traverses the faces or the teeth of the gear from end to end. During the relative translation in opposite directions the cutter and gear are relatively fed toward each other and their direction or rotation is reversed at one end only of the relative translations, this end being that in which the cutter occupies the full line position and the L center of crossed axes is remote from the gear. By reason oi relatively feeding the cutter and gear at this end ofthe relative translations obiectionable interference to the relative feeding is largely avoided since the cutter and gear are in comparatively loose mesh at this time.

Figure le diagrammatically illustrates another machine forcarrying out the method. The ma.- chinc is quite similar to that shown in the Drummond Patent No. 2,270,421 and has the table I! which carries the gear and the head 5| which carries the circular gear-like cutter '52 in mesh and at crossed axes with the gear. The cutter is rotated and thereby rotates the gear. The gear and cutter are relatively translated preferably very rast by reciprocating the table l8- through the electric motor 53 and the gearing 54. The mechanism ior driving the cutter 52 and reciprocating the table I9 are preferably of standard construction. The electric motor for driving the cutter is reversed at one end only of the relative translations by a limit switch similar to the limit switch 24 and operated by suitable means, such as a dog, upon the table I9.

To effect relative feed of the gear and cutter toward each other, the table I! is adjusted vertically at one end only of the relative translations-i end being preferably-the same as the end at 'which the cutter driving motor is reversed.

The vertical adjustment is accomplished by the table elevating screw S5 which is driven by the ratchet feed mechanism 56 operated by the cam 51, which latter is driven by the electric motor 5I.l The ratchet reed mechanism 56 comprises the' ratchet plte t9, the pawlll engageable with the teeth of the ratchet plate, the arm 6l and the lever B2.: The arm is pivoted coaxially with the ratchet .y plate and has pivotally connected to one end the pawl B0 and is pivotally connected at the other end to the lever. The ratchet plate is connected tothe feed screw by the bevel pinion 63 secured 'to the iced screw and a suitable bevel gear meshing with the pinion and to which the plate is secured. The lever 62 carries intermediate its ends, the roller Bd which is engageable with the cam tl. The cam 5l is driven by the 'worin 6B upon the shalt BB, which latter in turn is driven by the electric motor 58. For controlling the operation oil the electric motor there is the limit switch el i'or starting the motor 53, this limit switch being actuable by the contact dog 6&2 upon its travel. There'is also the `*limit switch @u for stopping the electric motor ol, this latter limit switch being actuable by the cam lll which is driven in perfect synchronism with the cam 5l by the worm il upon the shaft. to.

In operation it will be seen that when the table is at one end o? its relative translation the con-f tact dog operates upon the limit switch 6l to cause the electric lmotor t@ to be started. As a result, the worms Bt and li are rotated in unison to rotate the cams 5i and 'le in unison. As s, result oi' the rotationoi the cam 5l the lever d@ is rocked, asis .also the arm Si; to advance the ratchet plate 5t and thereby turn the feed screw it to raise thetable and-consequently. the gear. The rotation of the cam la continues to the inert high point on' the cam'. at which time the limit switch t9 is operated ,to cause the electric motor to stop by denergizing the same.

What l claim as 'my invention is: l. The method of shaving the teeth of a narrow face width gear member which comprises rotatying the gear member and a circular gear-like cutter member in` mesh at crossed axes with the center of crossed axes passing through the cutter member adjacent one end thereof; reciprocating one of the members parallel to the axis of the gear member while the members are in mesh so that the center of crossed axes traverses the entire tace of they gear member. and relatively feeding the members toward each other at one end only of the reciprocations.

2. The method oi shaving the teeth of a narrow face width gear member which comprises rotat ing the gear member and a circular gear-like cutter member in mesh at crossed axes with the center o! crossed axes passing through the cutter member adjacent one end thereof, meanwhile eiecting a relative translation o! the members in oppositev directions so that the center of crossed axes traverses the entire face of the gear member and reciprocates through a distance appreciably greater than the width of the gear member. and relatively feeding the memberstoward each other only at the end of the relative translations when the center of crossed axesI is rela tively remote from the gear member.

3. The method of shaving the teeth of a narrow face width gear member which comprises rotatln'g the gear member and a circular gear-like cut the table when the table is at one end of 7 ter member in mesh at crossed axes with the center of crossed axes passing through the cutter member adjacent one end thereof. meanwhile eiecting a. relative translation ot the members in opposite directions so that the center of crossed axes traverses the entire face of the gear member and reciprocates through a distance appreciably greater than the width of the gear member, and relatively feeding the members toward each other and reversing the direction of rotation of the members only at the end of the l0 Number relative translations when the center of crossed f The following references are ot record the ille of this patent:

UNITED STATES PATENTS Name Date Drummond Jan. 20, 1942 axes is relatively. remote 

